This invention relates to electrostatic copiers, and more particularly to the cleaning devices of such copiers.
In electrostatic copiers it is known to electrostatically charge the photosensitive surface of an endless, usually cylindrical, travelling carrier, thus forming a latent image of an original to be reproduced. Particles of toner powder with spherical toner carrier particles are attracted to the charged areas and adhere thereto, forming a layer. Thereupon, this layer is transferred to a copy carrier and forms thereon the desired image, i.e., a reproduction of the original. This completes a copy cycle of the machine.
Before the next copy cycle can begin, the surface of the travelling carrier must be cleaned to remove from it any residual particles and/or contaminants that may still adhere to it. For this purpose it is known to use a cleaning web or tape which contacts the carrier surface to wipe the particles off the same. A mechanism advances the tape from a supply to a take-up, so that constantly new, clean tape portions contact the carrier surface to wipe it clean.
These known cleaning arrangements are simple and inexpensive to construct, of small size and therefore readily accommodatable in the often cramped confines of the copying machines, and in general they are relatively easy in their effect on the very easily damaged photosensitive surface of the carrier.
In certain circumstances they can, however, cause severe scratching of this surface.
The spherical carrier particles are comparatively hard and large. They should theoretically, be completely removed from the photosensitive surface by the time the portions thereof from which the image has been transferred to the copy carrier, reaches the cleaning tape. However, at times some of these carrier particles do continue to adhere to the photosensitive surface and are carried to the cleaning tape, the wiping action of which then moves these carrier particles around on the surface where they can cause very substantial damage by scratching.